Negative active material for rechargeable lithium battery, method preparing the same and rechargeable lithium battery including the same

Abstract

In an aspect, a negative active material for a rechargeable lithium battery including surface modified silicon oxide particles is disclosed.

What is claimed is: 
     
       1. A negative active material comprising:
 surface modified silicon oxide particles having a bulk formula represented by SiO x  (0.6≤x≤0.95), said particles comprising a surface and a surface region having a depth wherein the depth of the surface region is from 2 nm to 40 nm from the surface, wherein a silicon-to-oxygen ratio (Si/O ratio) of the surface region ranges from about 1.8 to about 2.0, wherein oxygen has an increasing concentration profile within the depth from the surface, whereas silicon has a decreasing concentration profile within the depth from the surface, wherein the negative active material has an average particle diameter ranging from about 0.1 μm to about 100 μm, and wherein the negative active material has a specific surface area ranging from about 5 m 2 /g to about 500 m 2 /g. 
 
     
     
       2. The negative active material of  claim 1 , wherein the depth of the surface region is from 5 nm to 20 nm from the surface. 
     
     
       3. The negative active material of  claim 1 , wherein the depth of the surface region is from 5 nm to 15 nm from the surface. 
     
     
       4. The negative active material of  claim 1 , wherein the silicon content of the surface is measured using X-ray photoelectron spectroscopy (XPS) with ion beam sputtering. 
     
     
       5. The negative active material of  claim 1 , wherein the oxygen content of the surface is measured using X-ray photoelectron spectroscopy (XPS) with ion beam sputtering. 
     
     
       6. The negative active material of  claim 2 , wherein the Si/O ratio ranges from 1.8 to 2.0. 
     
     
       7. The negative active material of  claim 1 , wherein the bulk formula is represented by SiO x  (0.6<x<0.95). 
     
     
       8. The negative active material of  claim 1 , wherein the negative active material has a specific surface area ranging from 5 m 2 /g to 500 m 2 /g. 
     
     
       9. The negative active material of  claim 8 , wherein the negative active material has a specific surface area ranging from about 10 m 2 /g to about 40 m 2 /g. 
     
     
       10. The negative active material of  claim 1 , wherein the surface modified silicon oxide particles further comprise a coating or deposits of a carbonaceous material on the surface thereof. 
     
     
       11. The negative active material of  claim 1 , further comprising a carbonaceous material mixed with the surface modified silicon oxide particles. 
     
     
       12. A rechargeable lithium battery comprising:
 a negative electrode; 
 a positive electrode; and 
 an electrolyte, 
 wherein the negative electrode comprises:
 a current collector comprising two major surfaces; and 
 the negative active material of  claim 1  formed on at least one of the two major surfaces. 
 
 
     
     
       13. The rechargeable lithium battery of  claim 12 , wherein the current collector comprises at least one selected from the group consisting of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, and a polymer substrate coated with a conductive metal.